1. Technical Field
An aspect of the present disclosure relates to a printer employing a paper feed roller and a tractor as a transfer mechanism for transferring continuous paper, and more particularly, to a transfer control method of continuous paper and a printer which transfers the continuous paper with high precision.
2. Related Art
Heretofore, in printers capable of printing continuous paper with sprocket holes (engagement holes) formed on both ends thereof, a tractor and a paper feed roller are used as a transfer mechanism for transferring the continuous paper. The tractor includes tractor pins (engagement portions) which can be inserted into the sprocket holes formed along a longitudinal direction of the continuous paper, a tractor belt with the tractor pins formed on its outer circumference at certain intervals, and a drive sprocket and a driven sprocket with the tractor belt mounted therebetween. The paper feed roller is disposed between a printing position and the tractor.
A printer including a tractor and a paper feed roller is disclosed in JP-A-2011-168365. The printer disclosed in JP-A-2011-168365 transfers the continuous paper by use of the tractor as a main feed unit until a leading end of the continuous paper fed from the tractor side is delivered to the paper feed roller, and the paper feed roller as the main feed unit after the continuous paper is delivered to the paper feed roller. Using the paper feed roller as the main feed unit during printing is preferable to the high precise printing.
Further, the printer disclosed in JP-A-2011-168365 controls a transfer amount of the continuous paper by detecting a rotational amount of the paper feed roller when the paper feed roller is used as the main feed roller. If the continuous paper slips on the paper feed roller due to the increased transfer load of the continuous paper, the actual feeding amount is decreased relative to the actual feeding amount (set feeding amount) which can be calculated from the rotational amount of the paper feed roller, which creates a transfer error. Accordingly, in the printer disclosed in JP-A-2011-168365, the actual feeding amount of the continuous paper is calculated by detecting a driven amount of the tractor whenever the printing corresponding to one page is performed, and a difference between the calculated set feeding amount and the calculated actual feeding amount is calculated from the rotational amount of the paper feed roller. When the continuous paper is fed to a next page, the set feeding amount is compensated by the amount to eliminate the difference, and the rotational amount of the paper feed roller is controlled according to a compensation value.
As described in the printer disclosed in JPA-2011-168365, the transfer control method can realize the high precise printing, since the paper feed roller is used as the main feed roller during printing. Further, the transfer precision can be improved, since the feeding amount to feed the paper to the next page is compensated to eliminate the transfer error created during printing. However, the transfer control method does not consider the transfer error in a transfer section, but consider the transfer error during printing. For this reason, after the printing is completed, it is not possible to eliminate the transfer error which is created when the paper is fed to the next page. Further, since it is not possible to prevent accumulation in the transfer errors, a printing start position shift may be increased at a next page in a case where the transfer amount is high due to the many number of pages.